Method of making copper-titanium alloys



Patented July 28,- 1936 v UNiTED STATES PATENT OFFICE METHOD OF MAKING COPPER-TITANIUM .ALLOYS George F. Comstock, Niagara Falls, N. Y., as

signor to The Titanium Alloy Manufacturing I(ompany, New York, N. Y., a corporation of aine No Drawing. Application A ril 18,1934, Serial No. 721,153 7 24 Claims. (01. 75-135) My invention relates to improved methods in copper than the pure metal and dissolves faster;

the production of copper-titanium alloys in which copper is the predominant constituent, and more particularly to novel methods by which so that it is much more readily stirred into the hence the loss by oxidation and drossing is not particularly serious.

Copper-titanium master alloys have heretofore 5 the molten copper may be alloyed with titanium been made by reducing titanium from its oxide 5 or its compounds with the use of different flux with aluminum either by a'thermit reaction or materials that afford a coating for the metals in in a bath of copper in an electric furnace. Althe molten state to protect same from oxidation loys made by such methods always suffer from which becomes excessive where the molten metthe objection of a residual aluminum content als are exposed directly to the atmosphere. that is not desired in age-hardening copper al- 10 Difficulties have long been experienced in castloys. An appreciable proportion of the titanium ing copper, since perfectly pure copper when in copper-titanium alloys made by electric or melted in contact with air absorbs oxygen which alumino-thermic methods is nearly always in produces a somewhat porous condition in the inp the form of nitride that is also objectionable,

l5 got;. in like manner titanium rapidly absorbs since titanium so combined is not effective for 5 nitrogen and oxygen from the air, and-alloys age-hardening, and the nitride is infusible therewith higher amounts of titanium tend-to form by causing dirtiness and slow solubility of the surface films that greatly increasecasting difmaster alloy in a copper melt. Hence titanium flculties. 1 alloys of this nature have not been used suc- The objects of my invention are, among other cessfully for the manufacture of age-hardening things, to provide new and simplified methods of copper alloys. producing these copper-titanium alloys economi-t Very good copper-titanium master alloys may cally, without loss of copper and titanium, parbe. made by melting thevtwo pure metals toticularly of titanium, so as to obtain pure alloys gether under vacuum, but this process is expenfree from oxides, nitrides or carbides that readily sive and difficult to carry out on a large or in- 25 form when the molten metals are in contact with dustrial scale. The process is much simplified the atmosphere or carbonaceous gases. if a controlled atmosphere is substituted for a Titanium is useful for the production of agevacuum, but atmospheres of carbonaceous gases hardening copper alloys of good electrical conor nitrog n a impractical on c t of the ductivity and strength, but when the addition of. affinity of titanium for nitrogen and carbon;

- pure titanium in the metallic form to a bath hydrogen and helium both dissolve in the copof molten copper is attempted, it is very diflicult per, thereby producing a master alloy from which to secure good recoveries of titanium in a clean sound copper alloy castings cannot be made; and alloy. Since titanium is of much lower specific the use of argon or other rare gases is too exgravity and higher melting point than copper, it pensive. 35 floats on the latter, and a large portion of the I have discovered improved methods for the titanium burns in the air forming a refractory production of copper-titanium master alloys of dross before it dissolves in the copper. Such high purity by mixing and melting the two pure method may of course be carried out under metals that involves the use of a thick layer of 40 vacuum, but this is impractical commercially a novel suitable slag or flux on top of the 40 since no foundries at present are equipped to melt molten copper in order to protect the titanium the constituent metals in that way. metal floating on the copper from the action of The amount of titanium used for age-hardenthe atmosphere, while it is dissolving in the coping copper is usually less than 2%, and never per bath below.

45 more than 3 or 4%, so that the use of a master- My methods are ch ap a require no p alloy containing 25 to 30% titanium and the balslve equipment or materials, and may be easily ance copper is practical for the production of carried out on any scale desired. If certainiesthe age-hardening alloys under normal foundry sential precautions hereinafter described are conditions. carefully observed, the production of a clean,

For example, for making 100 pounds of a 2% high-grade copper-titanium master alloy con- 50 titanium alloy, it-would be necessary to add only taining no titanium-nitride, aluminum, hydroabout 10 pounds of a 25% master alloy to 92 gen, or other objectionable impurities is atpounds of molten copper including an allowance tained and the recovery of the titanium metal for oxidation losses, and this addition is not too usedis excellent.

large to be absorbed by the melt within a reason- For the successful working of my improved 5 able time before pouring. The master alloy conmethods the slag used must be very fluid at the taining to copper is much heavier than fusion temperature of copper and the copperpure titanium, and its melting point is'about titanium alloys to be made (about 2000 to 2200 6 1200 s o p ed to 800 C. for titanium, F.), and yet it must not decompose or volatilize rapidlyat those temperatures. Also it must of course not react chemically with titanium or carry oxygen or nitrogen to the metal beneath.

Owing to the. high reactivity of titanium with oxides such as silica at temperatures of 2000 F. or over, it is necessary that no silicates or other oxides should be present in this slag, and it is equally important that no easily reduced metals should be present, since such metals would be reduced by the titanium and contaminate the' copper-titanium alloy. 1 have found that chlorides and fluorides of the alkali and alkaline-earth (1) 80% CaF2+10% (2) 90% CaFz+10% (3), 85%.CaFz+15% (4) 90% CaFz+10% S1C12 BaClz NaCl Mixture No. 1 I found to be somewhat preferable to the others in fluidity and stability, and was most used, but was generally modified to the extent of decreasing the proportion of calcium fluoride to equal four (4) parts to one part (1) of each of the other ingredients. As the sodium fluoride and calcium chloride tend to be lost from the slag during use, they should be replenished duration an operation if the slag seems to be los- ..ing fluidity. I 40 Since these-slags at 2000 F. and above were extremely corrosive on all kinds of refractories that include clay and magnesia, I found it quite necessary to practicemy methods with a pure Acheson graphite crucible. With other kinds of crucibles, such as thoseknown as Plumbago containing a clay bond, the slag absorbed oxides from the crucible and became viscous, so that the titanium metal was held in the slag. The titanium then oxidized and instead of dissolving cleanly in the alloy beneath, it formed an infusible crust under the slag thereby causing a very low recovery of titanium in the fluid alloy.

To prevent any such trouble from oxidation I found it advisable to keep the pure Acheson graphite crucible covered, preferably with a flat piece of graphite, although the cover might be removed temporarily in order to add the titanium and for stirring, etc. In this way a reducing atmosphere was maintained most of the time in the crucible. I also found it of advantage to use a'narrow, deep, crucible rather than a. shallow broad one so that there would be less surface of the melt exposed to the air.

During the operation the temperature of the furnace should be maintained sufficiently high to keep the slag and alloy beneath in a fluid condition, but not so high as to cause the slag to fume very strongly. I

As illustrative examples of successful operations in making high-grade copper-titanium alloys according to my'methods, the following descriptions are given:-

Example 1.--A piece of an Acheson graphite electrode about 4 in. in diameter was first hollowed out in the form of a crucible about 6 inches NaF+10% CaClz I deep with walls about inch thick, and placed inside a s'ilicon-caroidetube, which in turn was set in a gas-fired furnace. About 400 grams of pure scrap copper were then placed in the bottom of this crucible and covered with about 7 5 ounces of a mixture of calcium fluoride, 10% sodium fluoride, and 10% calcium chloride (MixtureNo. -1)

The gas fire was lit, and in about 1 /2 hours the copper and slag were molten at a temperature of about 2200 F. More slag was then added. making a total quantity of 10 ounces used. When this slag became fluid, small solid lumps of metallic titanium, together with pieces of pure copper scrap were added gradually to the crucible. These additions were made every 10 to 15 minutes extending over a period of about 1% hours, the total quantity of titanium added being 261 grams, and the total copper used being 870 grams. The final addition was of copper only. 0 The metals sank readily through the slag except in a few instances when a lump had to be poked in with a copper rod. The same rod was alsoused for stirring. The crucible was kept covered with a brick between additions, and the 25 temperature was maintained between 2200 and 2360 F. After the last addition had been stirred in, the fire was shut off, and the alloy allowed to solidify in the crucible. When cold, a clean button was easily separated from the slag. It weighed 1081 grams,- and I found it contained 24.54% titanium at the top, and 16.50% at the bottom.

' Taking the average titanium content as 20.52 this indicated a recovery of of the titanium added; or assuming that the 50 gram loss of metal used was all titanium, the average analysis would be 19.5%titanium, and the recovery 81%.

Example 2.-A piece of an Acheson graphite electrode about 6 inches in diameter and 16 inches long was first machined into the form of a crucible 14 inches tall, 4 inches inside diameter. at the bottom and 4 inches at the top, and with walls about inch thick. This crucible was thoroughly coated on the outside with a plastic refractory held in place with wire mesh, and after drying it was heated slowly in a gas-fired furnace.

Ten pounds of pure copperscrap were charged into the crucible, and before this was melted about ten ounces of a slag mixture, composed of 4 parts calcium fluoride, 1 part calcium chloride, and 1 part sodium fluoride were thrown in to cover the copper. About two hours after starting the furnace the copper and slag were melted at a temperature of about 2000 F., and another addition of 10 ounces of slag was made, and the cruciblewas covered with a flatpiece of graphite. About half an hour later, when the slag was thoroughly fluid again, metallic titanium. in solid rough lumps of about to 1 inches size was 60 added. Every ten minutes, about /2 pound of titanium was dropped through the slag; and about every half hour the slag was replehished. On' one occasion the slag addition consisted of A pound NaF and 4 pound CaClz, to increase the fluidity. Before adding a batch of titanium the bath was stirred with a pure graphite rod to make sure that the previous batch had dissolved. When 3 pounds had been added, the subsequent additions'were accompanied by copper, to the ex- 70 tent of about 11 ounces copper to 8 ounces titanium, and these additions were spaced-15 minutes apart. The total amount of copper used was 14 pounds, and the total of titanium was 6 pounds, with 3 pounds of slag. About 25 minutes after 75.

the last addition, the contents of the crucible were poured outinto iron ingot molds, the alloy and slag being all very fluid and separating cleanly from each other. The alloy recovered weighed 19 pounds, and the first ingot was found to contain 28.62% titanium while the'last one contained amount of slag used was four pounds.

29.16%. The recovery of titanium therefore was 92%, indicating a reasonably low oxidation loss in the slag.

Example 3.--When the titanium available for use in making this alloy is too finely divided to sink rapidly through the .slag used, it may be packed in sections of copper tubing of convenient size with both ends closed. These capsules may then be added through a deep bath of slag just as lumps of titanium were added in the previous examples. In one instance tubing of 1 inch outside diameter and 0.042'inch wall thickness was used, 22 capsules about 4% inches long being prepared and filled with 1782 grams of fine metallic titanium globules. The copper charge consisted of 2486 grams of scrap, and 1672 grams in the form of tubing.

The same crucible and furnace were used as described in Example 2, and the same kind of slag. namely 4 parts calcium fluoride, 1 part sodium fluoride and 1 part calcium chloride. A little of the slag was placed in each capsule to v displace some of the air within.

The operation of melting was carried out in the same way as has been heretofore described, two capsules being added about every five minutes with occasional slag additions. The total The alloy produced weight 5330 grams after cleaning and contained 26.5% titanium, which represents a recovery of about 79% of the titanium added.

The loss is naturally higher in this method than in Examples 1 and 2 because of oxidation of the fine titanium by the air unavoidably entrapped between the particles inside the capsules.

When fine titanium metal was added directly to the slag, without being packed in copper capsules, it failed to sinkthrough the slag with sufficient rapidity and became oxidized thereby making the slag pasty and interfering with the proper alloying action. Likewise when a crucible containing a clay binder was used without being carefully: covered, the same pastiness of the slag resuited so that titanium was held in it and oxidized before alloying. In both instances a large proportion of the titanium was lost in the form of a dirty infusible product, that gave recoveries of only 10 to- 25% of the titanium in a form that could be used for treating copper.

Example 4.Another method of utilizing fineiy-divided titanium metal for making high-grade copper-titanium is to place the titanium in a puregraphite crucible in layers alternating with layers of finely divided copper, such as shot or turnings, and then cover the charge with suffi cient non-oxidizing slag so that on heating the interstices between" the metal particles may be filled with sl'agreplacing the air with still enough slag leftto form an effective cover on top.

Following this method, 4585 grams of copper shot and-1965 grams of titanium globules were charged in alternate layers inthe same kind of crucible described in Example 2, the top and bot" tom layers-being copper. The slag used was 4- pounds- -of the same mixture of 4 parts'calcium fluoride, l-part sodium fluoride, and 1 part calcium chloride. The crucible was covered. with a graphite block, and heated about 2 /2 hours. The

"poured into molds.

. titanium.

charge was then found to be fluid and was then The alloy product weighed 5439 grams and tion is not to be confined to the particular slag I formulae mentioned in the examples, nor to any definite composition of copper-titanium alloy. Any halogen salts of alkali or alkaline-earth metals free from oxygen may be employed in my methods, although I believe that a mixture com posed of at least 50% calcium fluoride would be most convenient to use for reasons of economy and resistance to volatilization.

To obtain proper fluidity in the slag without using excessively high temperatures, there should beat least 10% of a lower-melting salt added to the calcium fluoride; and probably 20 to of such a common and cheap salt, such as sodium chloride, or of a mixture of'calcium chloride and sodium fluoride, added to 65 to 80% of calcium fluoride, would form the most appropriate mixture for protection of the titanium in making high-grade copper-titanium alloys.

Other modes of applying the principles of my invention may be used in place of these described, and various changes may be made in the ingredients of the slag formulae and the methods disclosed that maintain the protective non-oxidizing coating for the titanium in the production of copper alloys of high titanium content provided the ingredients or steps stated in the appended claims, or their equivalents be employed.

I claim as my invention:-

1. In a method of making copper-titanium alloys by melting together the pure metals, the step which consists in immersing the titanium in a flux comprising a, fluid fused halogen salt of an alkaline-earth metal to prevent oxidation of the 2. In a method of making copper-titanium alloys by melting together the pure metals, the step which consists in immersing the titanium in a fluid fused mixture of halogen salts of alkali and alkaline-earth metals to prevent oxidation of l the titanium.

3. In a, method of making copper-titanium alloys by melting together the pure metals, the step which consists in immersing the titanium to prevent oxidation thereof in a fused mixture comprising calcium fluoride and a relatively smaller amount of an alkali-metal chloride.

4. In a method of making copper-titanium alloys by melting together the pure metals, the step which consists in immersing the titanium to prevent oxidation thereof in a fused mixture comprising calcium fiuoride and relatively smaller amounts of an alkali-metal fluoride and an alkaline earth-metal chloride.

5. In a method of making copper-titanium alloys by melting together the pure metals, the step which consists in immersing the titanium to prevent oxidation thereof in a fused mixture comprising calcium fluoride not less than 50% and prevent oxidation thereof in a fused mixture comprising calcium fluoride from 65-to 80% and sodium chloridefrom 20 to 35%.

7. In a method of making copper-titanium alloys by melting together the pure metals, the

step which consists in immersing the titanium to prevent oxidation thereof in a fused mixture comprising calcium fluoride from 65 to 80% and a metallic charge out 'of contact with the atmos-' phere to a temperature sufficiently high to effect the-solution of the titanium in the copper.

9. A method of making alloys containing from 10 to 40% titanium with the balance substantially copper, which comprises superimposing a nonoxidizing flux composed of halogen salts of alkalinesearth metals above the copper and melting same, then immersing metallic titanium in the molten slag formed, and then heating the charge sufliciently high to dissolve the titanium below the molten slag to alloy with the subjacent molten copper.

10. A method of making alloys containing from 10 to 40% titanium with the balance substantially copper, which comprises superimposing a nonoxidizing flux composed of amixture of calcium fluoride not less than 50% and relatively smaller amounts of an. alkali-metal fluoride and an alkaline earth-metal chloride above the copper and melting same, then immersing metallic titanium in the molten slag formed, and then heating the charge sufliciently high to dissolve the titanium below the molten slag to alloy with the subjacent molten copper.

11. A method of making alloys containing from 10 to 40% titanium with the balance substantially copper, which comprises superimposing a non-oxidizing flux composed of a mixture of calcium fluoride from 65 to 80% and sodium chloride from 20 to 35% above the copper and melting same, then immersing metallic titanium in the molten slag formed, and then heating the charge sufiiciently high to dissolve the titanium below the molten slag to alloy with the subjacent molten copper.

. 12. A method of making coppentitanium alloys which comprises melting a quantity of copper in a crucible of pure graphite, maintaining a superimposed fluid' non-oxidizing slag .composed of fused halogen salts of alkali and alkaline-earth metals orithe molten copper, and then immersing metallic titanium in the slag to dissolve in the molten copper through said fluid slag.

13. A method of making copper-titanium alloys which comprises melting a quantity of copper in a covered crucible of pure graphite, maintaining a superimposed fluid non-oxidizing slag composed of fused halogen salts of alkali and alkalineearth metals in a reducing atmosphere on the molten copper, and thenv immersing metallic titanium in the slag to dissolve in the molten copper through saidfluid slag.

14. A method of making high-grade coppertitanium alloys which comprises maintaining a fluid non-oxidizing slag composed of fused halogen salts of alkali and alkaline-earth metals in a covered crucible of pure graphite at a temperature above the melting point of copper, add- Q 2,049,291" s 'ing thereto solid pieces of themetals copper'and titanium, and then melting said metals together belowthe slag. I g

15. A flux for usein making copper-titanium alloys in which copper is the major constituent, which consists in a fluid fused mixture of calcium fluoride as the major ingredient and a smaller amount of an alkali-metal chloride.

16. A flux to be used in contact with molten copper-titanium alloys in which copper is the major constituent, comprising a fused mixture of calcium fluoride as the major ingredient and relatively smaller amounts-of an alkali-metal fluoride and calcium chloride, said flux being fluid at temperatures from 2000 to 2300 F.

1'7. A-flux for use in making copper-titanium alloys in which copper isthe major contituent,

" which consists in a fluid fused mixture of 'calcium fluoride from 65 to 80% and sodium chloride from 20- to 35%.

18. A flux to be used incontact with'molten copper-titanium alloys in which copper is the major constituent, comprising a fluid fused mixture .of calcium fluoride from 65 to 80% and calcium chloride and sodium fluoride from 20 to I 19. In a method of making copper-titanium alloys by melting together the pure metals, the

step which consist in immersing the titanium to prevent oxidation thereof in a fusedvmixture comprising calcium fluoride and a relatively smaller amountof an alkaline-earth metal chloride.

20. In a method of making copper-titanium alloys by melting together the pure metals, the step which consists in immersing the titanium to prevent oxidation thereof in a fused mixture comprising calcium fluoride and relatively smaller amounts of an alkli-metal fluoride and an alkaline-earth metal chloride.

21. A method of making alloys containing from 10 to 40% titanium with the balance substantially copper, which comprises superimposing a nonoxidizing flux composed of a mixture of calcium fluoride not less than 50% and relatively smaller amounts of an alkali-metal fluoride and an alkaline-earth metal chloride above the copper and melting same, then immersing metallic titanium in the molten slag formed, and then heating the charge sufliciently high to dissolve the titanium below the molten slag to alloy with the subjacent molten copper.

22. A flux to be usedin contact with moltenv copper-titanium alloys in which copperis the major constituent comprising a fused mixture of calcium fluoride as the major ingredient and relatively small amounts of an alkali-metal fluoride and an alkaline-earth metal chloride,-said copper-titanium alloys in which copper is the main constituent comprising a fused mixture of calcium fluoride and relatively small amounts of an alkali-metal fluoride and an alkaline earth metal chloride. N

24. A flux to be used in contact with molten copper-titanium, alloys in which copper is the 'main constituent comprising a fused mixture of calcium fluoride from 65 to 80% and sodium chlo-' ride from 20 to 35%, said flux being fluid at tem-' peratures from 2000" to 2300" F.

GEORGE F. coms'rocx. 

